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A Question About Time Travel & Aging

  1. Aug 26, 2017 #1
    Let's assume time travel is possible and we are travelling. We jumped to a TARDIS sort of machine in August 26, 2017 and go to August 26, 2000 then lived there for 4 years untill August 26, 2004. So when we come back to August 26, 2017 would we be 4 years older or be the same age we were before travelling?

    I know it is kind of a lame question but that'd be amazing if you answered this.Thank you already
  2. jcsd
  3. Aug 26, 2017 #2
    You would still have aged 4 years from 2000-2004. Even with "real" scientifically proven time-dilation effects the difference in years elapsed is relative to other observers with their clocks ticking at different rates, when you have a clock/calendar with you that says a year passed you age a year, even if someone else's clock says 10 years passed for them and they are 10 years older...
  4. Aug 26, 2017 #3
    This involves one of the paradoxes involved with the idea of reverse time travel, which hint that it cannot actually be possible.
    Suppose that after your 4 year stint away from base, you return to just a few minutes before you originally left.
    Now there will be two of you in the same place, one being four years older than the other.
    Which one is the 'real' you, and where did the additional matter come from which makes the other copy of you?
  5. Aug 26, 2017 #4
    Those aren't paradoxes. They are both the "real" you, and there isn't any extra matter, you are counting the same matter twice.
  6. Aug 26, 2017 #5
    That doesn't make any sense to me. If you could return to a point on a timeline shortly before you left there would be two of you and two machines that you used to "transport" through time existing in one time up until the time you originally left.
  7. Aug 26, 2017 #6
    Screen Shot 2017-08-26 at 4.08.14 PM.png

    It's like this. The string appears three times along the blue line. But it is only one string.
  8. Aug 26, 2017 #7
    In the bars above the "have something to add?" box there is a picture next to the smiley face...
  9. Aug 26, 2017 #8
    But that only lets me input a URL, not upload a pic I just made. I found what I needed by editing the post.
  10. Aug 26, 2017 #9
    I see says the blind man to the deaf ears.
    I thought about virtual existence AKA virtual particles when I wrote my response. Very big "IF" you could borrow matter from the future briefly and deposit it in a time before you took it, it would all balance out... very big if.
  11. Aug 26, 2017 #10
    It isn't virtual. You need to think of the object as a 4 dimensional structure. It's passage through time is part of it's identity. A time machine allows the strings personal timeline to travel contrary to an external viewer's timeline. The paradox doesn't start unless the future timeline somehow contradicts what it's own time did.
  12. Aug 26, 2017 #11
    If you only count it once there still is a problem.
    If you having returned you decide not to do that trip?
    Last edited: Aug 26, 2017
  13. Sep 1, 2017 #12

    stefan r

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    Gold Member

    Or if you still want to do the trip. Enough cycles will collapse into black hole.
  14. Sep 13, 2017 #13
    The fact that you returned proves that you do/did (there is no difference) the trip. There is no choice anymore.
  15. Sep 13, 2017 #14
    Then it becomes impossible for you to have had a life which lead to your original decision to do it.
  16. Sep 14, 2017 #15
    I think you mean it is impossible to have had a life that doesn't lead to the original decision to do it. Everything else makes no sense.
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